Walk through the structured form array, adding any required properties to
each element and mapping the incoming input data to the proper elements.
Also, execute any #process handlers attached to a specific element.

Code

<?php
function_form_builder_handle_input_element($form_id, &$element, &$form_state) {
if (!isset($element['#name'])) {
$name = array_shift($element['#parents']);
$element['#name'] = $name;
if ($element['#type'] == 'file') {
// To make it easier to handle $_FILES in file.inc, we place all
// file fields in the 'files' array. Also, we do not support
// nested file names.
$element['#name'] = 'files[' . $element['#name'] . ']';
}
elseif (count($element['#parents'])) {
$element['#name'] .= '[' . implode('][', $element['#parents']) . ']';
}
array_unshift($element['#parents'], $name);
}
// Setting #disabled to TRUE results in user input being ignored, regardless
// of how the element is themed or whether JavaScript is used to change the
// control's attributes. However, it's good UI to let the user know that input
// is not wanted for the control. HTML supports two attributes for this:
// http://www.w3.org/TR/html401/interact/forms.html#h-17.12. If a form wants
// to start a control off with one of these attributes for UI purposes only,
// but still allow input to be processed if it's sumitted, it can set the
// desired attribute in #attributes directly rather than using #disabled.
// However, developers should think carefully about the accessibility
// implications of doing so: if the form expects input to be enterable under
// some condition triggered by JavaScript, how would someone who has
// JavaScript disabled trigger that condition? Instead, developers should
// consider whether a multi-step form would be more appropriate (#disabled can
// be changed from step to step). If one still decides to use JavaScript to
// affect when a control is enabled, then it is best for accessibility for the
// control to be enabled in the HTML, and disabled by JavaScript on document
// ready.
if (!empty($element['#disabled'])) {
if (!empty($element['#allow_focus'])) {
$element['#attributes']['readonly'] = 'readonly';
}
else {
$element['#attributes']['disabled'] = 'disabled';
}
}
// With JavaScript or other easy hacking, input can be submitted even for
// elements with #access=FALSE or #disabled=TRUE. For security, these must
// not be processed. Forms that set #disabled=TRUE on an element do not
// expect input for the element, and even forms submitted with
// drupal_form_submit() must not be able to get around this. Forms that set
// #access=FALSE on an element usually allow access for some users, so forms
// submitted with drupal_form_submit() may bypass access restriction and be
// treated as high-privilege users instead.
$process_input = empty($element['#disabled']) && ($form_state['programmed'] || ($form_state['process_input'] && (!isset($element['#access']) || $element['#access'])));
// Set the element's #value property.
if (!isset($element['#value']) && !array_key_exists('#value', $element)) {
$value_callback = !empty($element['#value_callback']) ? $element['#value_callback'] : 'form_type_' . $element['#type'] . '_value';
if ($process_input) {
// Get the input for the current element. NULL values in the input need to
// be explicitly distinguished from missing input. (see below)
$input_exists = NULL;
$input = drupal_array_get_nested_value($form_state['input'], $element['#parents'], $input_exists);
// For browser-submitted forms, the submitted values do not contain values
// for certain elements (empty multiple select, unchecked checkbox).
// During initial form processing, we add explicit NULL values for such
// elements in $form_state['input']. When rebuilding the form, we can
// distinguish elements having NULL input from elements that were not part
// of the initially submitted form and can therefore use default values
// for the latter, if required. Programmatically submitted forms can
// submit explicit NULL values when calling drupal_form_submit(), so we do
// not modify $form_state['input'] for them.
if (!$input_exists && !$form_state['rebuild'] && !$form_state['programmed']) {
// Add the necessary parent keys to $form_state['input'] and sets the
// element's input value to NULL.
drupal_array_set_nested_value($form_state['input'], $element['#parents'], NULL);
$input_exists = TRUE;
}
// If we have input for the current element, assign it to the #value
// property, optionally filtered through $value_callback.
if ($input_exists) {
if (function_exists($value_callback)) {
$element['#value'] = $value_callback($element, $input, $form_state);
}
if (!isset($element['#value']) && isset($input)) {
$element['#value'] = $input;
}
}
// Mark all posted values for validation.
if (isset($element['#value']) || (!empty($element['#required']))) {
$element['#needs_validation'] = TRUE;
}
}
// Load defaults.
if (!isset($element['#value'])) {
// Call #type_value without a second argument to request default_value handling.
if (function_exists($value_callback)) {
$element['#value'] = $value_callback($element, FALSE, $form_state);
}
// Final catch. If we haven't set a value yet, use the explicit default value.
// Avoid image buttons (which come with garbage value), so we only get value
// for the button actually clicked.
if (!isset($element['#value']) && empty($element['#has_garbage_value'])) {
$element['#value'] = isset($element['#default_value']) ? $element['#default_value'] : '';
}
}
}
// Determine which element (if any) triggered the submission of the form and
// keep track of all the clickable buttons in the form for
// form_state_values_clean(). Enforce the same input processing restrictions
// as above.
if ($process_input) {
// Detect if the element triggered the submission via Ajax.
if (_form_element_triggered_scripted_submission($element, $form_state)) {
$form_state['triggering_element'] = $element;
}
// If the form was submitted by the browser rather than via Ajax, then it
// can only have been triggered by a button, and we need to determine which
// button within the constraints of how browsers provide this information.
if (isset($element['#button_type'])) {
// All buttons in the form need to be tracked for
// form_state_values_clean() and for the form_builder() code that handles
// a form submission containing no button information in $_POST.
$form_state['buttons'][] = $element;
if (_form_button_was_clicked($element, $form_state)) {
$form_state['triggering_element'] = $element;
}
}
}
// Set the element's value in $form_state['values'], but only, if its key
// does not exist yet (a #value_callback may have already populated it).
if (!drupal_array_nested_key_exists($form_state['values'], $element['#parents'])) {
form_set_value($element, $element['#value'], $form_state);
}
}
?>